remove the OpenGLWindow from charts

It is not necessary after disabling the 3D OpenGL charts.

Change-Id: I40fd398f2bcc5fc0d774e116ea243572cc36844d
Reviewed-on: https://gerrit.libreoffice.org/10325
Reviewed-by: Zolnai Tamás <zolnaitamas2000@gmail.com>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>
Reviewed-by: Jan Holesovsky <kendy@collabora.com>